By ASHLEY PARKER
The New York Times

WASHINGTON — As several of the eight senators taking part in a bipartisan effort to overhaul the nation’s immigration laws appeared on television Sunday to voice optimism about the negotiations, Sen. Marco Rubio, a member of the group, issued a strongly worded message of caution.

“No Final Agreement on Immigration Legislation Yet” was the headline, all in capital letters, of a statement released by his office Sunday.

An aide to Rubio, R-Fla., said his comments were not intended to suggest a deal was unlikely. Instead, his aim was to keep expectations in check until the details of the legislation are complete, and to urge the group to take the bill through “regular order,” which he says is necessary to garner public support. That process involves public hearings and amendments from other senators both in committee and on the Senate floor.

As the group of eight senators, split evenly between Democrats and Republicans, inches closer to a bill that would provide a path to citizenship for the 11 million illegal immigrants already in the country, Rubio seems determined to keep his conservative credentials intact.

Rubio was elected in 2010 as part of a tea-party wave and is considered an early contender for the Republican presidential nomination in 2016. Although that race is still far away, any Oval Office ambitions that Rubio has are likely to hinge, in part, on his success at selling an immigration overhaul to his party’s conservative base, which has resisted a path to citizenship for illegal immigrants.

Despite Rubio’s remarks, congressional aides and several of the eight senators say the group is still on track to introduce comprehensive immigration legislation when Congress returns from its break.

“It will be rolled out next week,” Sen. Lindsey Graham, R-S.C. and a member of the group, said on the CNN program “State of the Union” on Sunday.

In his statement, Rubio did not say the group was not proceeding apace; he simply counseled restraint.

“I’m encouraged by reports of an agreement between business groups and unions on the issue of guest workers,” he said. “However, reports that the bipartisan group of eight senators have agreed on a legislative proposal are premature.”

Rubio was referring to news reports on Saturday that the nation’s leading business and labor groups had agreed on a guest-worker program for low-skilled workers, one of the final sticking points in the talks among the eight senators.